Flexible endoscopes are used for many applications in medicine and technology. Flexible endoscopes of this kind comprise a flexible elongate shank, which is suitable for insertion into a cavity, for example a cavity inside the body or a cavity of a technical object. Generally, an endoscope lens is arranged at the tip of the endoscope shank to generate an image of a scene in the observed cavity. To record and transmit the endoscopic image from the distal end region (i.e. remote from the observer) to the proximal end region (i.e. near the observer) of the endoscope, it is possible, for example, to provide a coherent bundle of optical fibers extending inside the shank, or else an electronic image recorder, for example a CCD chip, which is arranged in the region of the distal end of the shank, and the signals of which are transmitted to the proximal end region via electrical lines extending inside the shank. Since there is generally insufficient light in the observed cavity, a light-guiding system can also be arranged inside the shank in order to convey light to the distal end of the endoscope, where it is used to illuminate the cavity. Furthermore, the endoscope shank can have one or more working channels through which endoscopic work instruments are passed from the proximal to the distal end region of the shank, and with the aid of which manipulations can be performed inside the cavity.
Endoscopic instruments are also known that comprise a flexible elongate shank which is likewise suitable for insertion into a cavity, for example a cavity inside the body or a cavity of a technical object. A flexible endoscopic instrument of this kind can be used to perform manipulations in the cavity and, for this purpose, can be designed for example as a grasping instrument for gripping and manipulating tissue or articles in the cavity inside the body or in the cavity of a technical object. For this purpose, a tool is arranged at the distal end of the flexible shank and can be operated from the direction of the proximal end of the shank by way of a transmission means extending inside the shank. A flexible endoscopic instrument of this kind generally does not have a dedicated optical unit for recording an endoscopic image, but it can in particular be used together with a flexible endoscope.
It is often desirable to be able to angle the distal end of the shank, i.e. the tip of the endoscope or of the endoscopic instrument, in order to make insertion of the endoscope or of the endoscopic instrument through a non-rectilinear channel easier, in order to be able to move the tip in a lateral direction inside a cavity, and in order to be able to vary the viewing direction of an optical unit arranged in the endoscope tip or the working direction of a tool arranged at the tip of the endoscopic instrument. For this purpose, the shank has a controllable portion, in particular a controllable end portion, that can be actively angled by a desired amount in a desired direction and, for this purpose, can be controlled from the direction of the proximal end of the endoscope or of the endoscopic instrument. The shank for a flexible endoscopic instrument does not itself need to have a tool and a transmission means, but instead can comprise, for example, a working channel into which a flexible endoscopic work instrument, which cannot be actively angled and which has such a tool, can be inserted as far as the distal end of the shank and optionally beyond this, such that the flexible work instrument can be angled with the aid of the shank.
To permit controllable angling of a portion of a shank of a flexible endoscope, it is known to design this with a base structure composed of individual, mutually pivotable segments that can be actuated by cable pulls or Bowden cables guided in the endoscope shank. For actuation, hand wheels in particular that are arranged on the handgrip of the endoscope are provided. According to US 2005/0131279 A1, each segment of a controllable portion of the endoscope shank is mounted so as to be pivotable relative to the next and/or preceding segment. To angle the shank portion in question or the endoscope tip, four cable pulls are provided which are guided as far as the endoscope tip from a control apparatus arranged at the proximal end. The cable pulls extend in the edge region of the segments and are offset in each case by 90° to each other relative to a longitudinal axis, such that control of the endoscope tip to a desired direction can be brought about by rolling up the corresponding cables in the control apparatus.
However, the cables of such cable pulls have a tendency to lengthen after repeated use, which adversely affects the controllability of the endoscope tip or makes it necessary to regularly re-tension the cable pulls. Resetting devices for setting the tension of the cable pulls are known, for example from DE 29 14 748 C2 and U.S. Pat. No. 4,203,430; however, resetting devices of this kind are associated with increased outlay in terms of construction and control. The necessary permanent tensioning of the cable pulls can also lead to a shortening of the shank, which can have an adverse effect on the controllability of the endoscope tip and indeed the properties of the endoscope shank, for example the flexibility or surface quality. The attainable angling also depends on the curvature of the whole shank portion through which the cable pulls are guided, with the result that there is no clear relationship between the position of a hand wheel, with which a cable pull can be rolled up, and the attained deflection angle of the endoscope tip. Curvatures of the endoscope shank also cause increased friction of the cable pulls, which likewise makes it difficult to control the angling. Finally, the cable pulls, particularly in longer shanks, may sever on account of the friction and of corresponding wear.
JP 07134253 A discloses an endoscope with a curvable portion comprising a plurality of segments which are interconnected in a hinged manner and which have threaded nuts, the latter cooperating with bolts that are connected to a flexible shaft. Near a proximal end of the curvable portion, a micromotor is arranged in the shank of the endoscope and sets the flexible shaft in rotation in order to control angling of the curvable portion. This entails quite a considerable outlay in terms of construction. Moreover, the load-bearing capacity of the shaft with the associated threaded nuts is not always sufficient. In addition, arranging a micromotor in an endoscope shank of small diameter, inside which there extend further lines and channels, is not readily possible, and it is also associated with considerable effort for reasons of accessibility to the motor for repair and maintenance purposes and, if appropriate, for cleaning and sterilization.